BaseCrush biscuits in a food processor or with the end of a rolling pin until they look like fine crumbs. Add melted butter and stir well to combine. Press mixture into the base of a 23cm springform cake tin. Bake for 10 minutes at 180 degrees celsius.

FillingUsing an electric mixer, beat cream cheese, caster sugar and mashed banana on medium speed until well blended. Add eggs, one at a time, beating well after each addition. Stir in walnuts. Pour mixture over biscuit base. Bake at 180 degrees celsius for 40 minutes. Turn off oven and allow cheesecake to cool with the door slightly ajar for at least 30 minutes. Remove from oven and gently loosen sides of cake tin. Do not remove sides yet. Sit on a wire rack and allow cheesecake to cool to room temperature.

When cheesecake is cool, melt chocolate pieces and butter in a bowl standing over a saucepan of hot water. Don't allow any water to come into contact with the chocolate. When melted, drizzle chocolate over the top of the cheesecake. Refrigerate for a minimum of 4 hours.